JP2006319950A - Image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image display device for adjusting the variable reference voltage of a counter electrode brought about by variation with time due to liquid crystal display devices without preventing the display of an input video signal. <P>SOLUTION: This image display device is configured to irradiate liquid crystal display devices with the rays of light from a light source, and to form and expansively project an optical image corresponding to a video signal. The image display device includes a reflection mirror for reflecting the rays of light with which the liquid crystal display devices are irradiated, an optical sensor located on the reflection mirror for detecting light intensity, a drive circuit that causes the liquid crystal display devices to be driven and a control circuit that controls the drive circuit based on the light intensity detected by the optical sensor. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image display device for enlarging and projecting an image of a display element to form an image on a screen.

  For example, in an active matrix type liquid crystal display element (also referred to as a liquid crystal display panel) used in a display device, an AC voltage that is inverted in a field period or a line period is applied between a picture element electrode and a counter electrode. However, there are variations in characteristics of the pixel electrode driving transistors, and the DC voltage of the counter electrode deviates from the inversion center voltage, causing flicker in the liquid crystal display element. In order to prevent this flicker, for example, Patent Document 1 discloses a technique for automatically adjusting a reference voltage applied to a counter electrode before shipment.

  Japanese Patent Application Laid-Open No. 2004-228688 discloses a technique for automatically adjusting the voltage of a common electrode by detecting flicker generated in an image projected on a screen from a liquid crystal projector by an optical sensor provided at the center of the screen.

Japanese Unexamined Patent Publication No. 6-30920 Japanese Patent Laid-Open No. 6-18842

  The above-mentioned Patent Document 1 is used in the production process, requires a separate computing device outside, and does not support adjustment of a single product. Therefore, it is difficult to adjust the image quality deterioration due to the temporal change of the reference voltage of the counter electrode caused by the liquid crystal display element after shipment, and the image quality deterioration due to the time change after shipment cannot be dealt with.

  Moreover, in patent document 2, since the optical sensor is located in the center of a screen, the shadow of the optical sensor in the image on a screen is easy to visually recognize.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a video display device capable of suitably correcting a change in image quality associated with a change with time of a display element.

  In the present invention, an optical sensor for detecting flicker is installed on a reflecting mirror that reflects light after irradiation to a display element installed in the video display device. Further, the optical sensor for detecting flicker may be arranged in the projection lens unit. As a result, it is possible to reduce the influence of the shadow of the optical sensor and the wiring of the optical sensor being projected on the screen.

  According to the video display device of the present invention, it is possible to provide a video display device capable of suitably correcting a change in image quality accompanying a change in display element over time.

  The best mode of the present invention will be described below with reference to the drawings. In each figure, elements having common functions are denoted by the same reference numerals, and those that have been described once will not be described repeatedly.

  First, before entering the description of the present invention, flicker caused by fluctuations in the reference voltage Vcom of the counter electrode will be described with reference to FIGS.

  FIG. 5 is a diagram showing the relationship between the reference voltage applied to the counter electrode of the liquid crystal display element and the inverted signal voltage applied to the pixel drive transistor, and FIG. 6 shows the image of the liquid crystal display element projected on the screen as an optical sensor. It is a figure which shows typically the AC component of the detection signal of the optical sensor at the time of detecting by (3). Usually, the display electrode of the liquid crystal display element is connected to the drain electrode of the pixel driving transistor, and the voltage loss between the drain and source of the pixel driving transistor is subtracted from the inverted signal voltage Vs applied to the source electrode of the pixel driving transistor. Since this voltage loss is applied to the display electrode, it is necessary to consider this voltage loss, but here, for ease of explanation, it is assumed that there is no voltage loss.

  In FIG. 5, the flicker occurs when the inverted signal voltage (voltage difference) with respect to the reference voltage Vcom of the counter electrode (not shown) is not equal between the positive case and the negative case. V1 represents a positive voltage (voltage difference) of the inverted signal applied to the pixel drive transistor (not shown) with respect to the reference voltage Vcom of the counter electrode, and V2 represents a negative voltage of the inverted signal applied to the pixel drive transistor. Indicates voltage (voltage difference).

  In the case of | V1 | <| V2 | (indicating an absolute value with ||), the positive and negative peak values of the inverted signal with respect to the reference voltage Vcom are significantly different, and flicker occurs. The detection signal of the optical sensor at this time has a waveform as shown in FIG. 6A, the level of the detection signal is high, and the positive and negative peak values are significantly different.

  Even in the case of | V1 |> | V2 |, as in the case of | V1 | <| V2 |, the positive and negative peak values of the inverted signal with respect to the reference voltage Vcom are significantly different, and flicker occurs. The detection signal of the optical sensor has a waveform as shown in FIG. 6B, the level of the detection signal is high, and the positive and negative peak values are significantly different.

  However, in the case of | V1 | = | V2 |, the positive and negative peak values of the inverted signal with respect to the reference voltage Vcom are equal, and flicker does not occur. The detection signal of the optical sensor (not shown) at this time has a waveform as shown in FIG. 6C, the level of the detection signal is low, and the positive and negative peak values are also equal.

That is, if the voltage (voltage difference) between the upper peak and the lower peak of the detection signal waveform in FIG. Hereinafter, the upper limit voltage of the voltage (voltage difference) between the upper peak and the lower peak where the flicker cannot be visually recognized is referred to as a flicker limit voltage and is denoted by a reference symbol V _FL . Although this voltage value varies depending on the projection optical system and the optical sensor, it can be considered that the voltage is almost the same between display devices of the same model, and this flicker limit voltage _VFL is measured and determined in advance using a predetermined measurement pattern. be able to. Therefore, when flicker occurs due to a change in the reference voltage Vcom of the counter electrode due to a change over time, the detection signal voltage is measured using the same measurement pattern, and a voltage (voltage) between the upper peak and the lower peak of the detection signal voltage is measured. changes in a predetermined direction the reference voltage Vcom by a predetermined step of the counter electrode so that the _{difference) V pp} is equal to or less than a flicker limit voltage _{V FL} (e.g., FIGS. 6 (a), i.e. the reference voltage to reduce the V4 in case of Vcom By changing the reference voltage of the counter electrode caused by the change over time caused by the liquid crystal display element, the adjustment of the reference voltage of the counter electrode to a good state (that is, the state where the flicker is not visually recognized) is performed (hereinafter referred to as “flicker”). Adjustments).

  Hereinafter, embodiments according to the present invention using the flicker adjustment described above will be described in detail.

  FIG. 1 is a block diagram of a liquid crystal display device according to a first embodiment, FIG. 4 is a diagram showing a control flow of a control circuit, and FIG. 7 is a diagram of a signal processing circuit.

  1, the liquid crystal display device is stored in a video processing circuit 60 that performs predetermined video processing on a video signal (not shown), a video signal 61 from the video processing circuit 60, and a built-in memory (not shown). A drive circuit 50 for driving the liquid crystal display element 73 based on a test pattern for adjusting flicker, and light intensity modulation of the light from the light source 72 according to the drive signal from the drive circuit 50 by the liquid crystal display element 73 to form An optical system 70 for enlarging the projected optical image (not shown) with the projection lens 100 and projecting it onto the screen 20, and a screen outer peripheral edge disposed on the outer peripheral edge of the screen 20 (for example, outside the effective display area of the screen 20). An optical sensor 10 that detects image light projected in the vicinity of the head, a signal processing circuit 30 that processes a signal from the optical sensor 10, and a signal processing circuit 30 The control circuit 40 for outputting a predetermined control information 41 according to the input signal, a switch 90 for instructing the start of a flicker adjustment control circuit 40, in constructed.

  The drive circuit 50 supplies a reference voltage Vcom applied to a counter electrode (not shown) of the liquid crystal display element 73 and an inversion signal applied to a pixel drive transistor (not shown), and an image is displayed on the liquid crystal display element 73. A raster pattern, which is a test pattern used for flicker adjustment, is stored in advance in a built-in memory (not shown), and has a function of forming an optical image according to a signal, and corresponds to control information 41 from the control circuit 40. The raster pattern for flicker adjustment of a designated color (for example, one of R, G, and B) is displayed at a designated display position on the liquid crystal display element 73 (that is, the installation position of the optical sensor 10). The drive circuit 50 includes a reference voltage generation circuit (not shown) that generates a reference voltage Vcom to be applied to the counter electrode of the liquid crystal display element 73. The reference voltage generation circuit (not shown) A reference voltage Vcom corresponding to a digital value (a digital reference voltage DVcom described later) included in the control information 41 input from the circuit 40) can be generated. When the liquid crystal display device is a three-plate type, a reference voltage generation circuit (not shown) is provided corresponding to each color. Further detailed description of the reference voltage generation circuit is omitted.

The control circuit 40 is composed of, for example, a microcomputer (usually referred to as a microcomputer) that is a calculation control means, and controls flicker adjustment according to a program built in a PROM (not shown). In a non-illustrated nonvolatile memory, for example, display position information (not shown) when displaying a raster pattern, color designation information (for example, one color of R, G, B) for specifying a raster pattern (see FIG. A digital flicker limit voltage DV _FL (not shown) corresponding to the flicker limit voltage V _FL , a digital reference voltage DVcom (not shown) corresponding to the reference voltage Vcom applied to the currently set counter electrode, And a digital voltage step DVstep (not shown) for changing the reference voltage at a predetermined voltage step. Control information is stored Do. As the reference voltage Vcom to be applied to the currently set counter electrode, a value set at the time of flicker adjustment at the time of factory shipment or the previous flicker adjustment is stored. When the liquid crystal display device is a three-plate type, a digital reference voltage DVcom is stored for each of R, G, and B.

  Further, the number of photosensors 10 arranged on the screen outline is determined based on the amount of light received by the photosensor. When the amount of light applied to one optical sensor is small, the signal amplitude output from the optical sensor is small, and it is difficult to make an accurate adjustment. Therefore, in such a case, a plurality of optical sensors are provided. As a result, the signal from the optical sensor is integrated, the output signal amplitude is increased, and the adjustment accuracy can be improved. In order to improve the adjustment accuracy, in addition to increasing the number of photosensors, the time for which the photosensors are irradiated with light may be lengthened.

  The liquid crystal display device shown in FIG. 1 normally performs predetermined signal processing on an input video signal (not shown) by a video processing circuit 60 and forms an optical image on a liquid crystal display element 73 by a drive circuit 50. The optical image is enlarged and projected onto the screen 20 by the optical system 70 to display the input video signal.

During the normal video display, for example, when the switch 90 is operated (not limited to this), the liquid crystal display device starts flicker adjustment. In other words, an optical image of a raster pattern that is a test pattern stored in the drive circuit 50 is displayed on the liquid crystal display element 73 by the drive circuit 50, and the raster pattern image is projected onto the screen 20 via the optical system 70. . Then, the image light of the raster pattern projected on the screen 20 is detected by the optical sensor 10 to measure the flicker of the liquid crystal display element 73 and according to the detection signal measured by the optical sensor 10, the liquid crystal display element 73. good condition flicker the reference voltage Vcom applied to the counter electrode from the current setting values are not visible (i.e., the detection signal voltage V _pp is the condition to be less flicker limit voltage V _FL) is automatically adjusted by the control circuit 40 in.

  Details of flicker adjustment will be described below according to the control flow of FIG. 4 and with reference to FIGS.

  When the control circuit 40 detects the operation of the switch 90, the control circuit 40 starts flicker adjustment. In step (hereinafter abbreviated as “S”) 501, the control circuit 40 first selects first color (for example, R color) designation information of a raster pattern from a memory (not shown), and drives as control information 41. Send to circuit 50. The drive circuit 50 generates a raster pattern corresponding to the color designation information based on the raster pattern stored in the built-in memory, and drives the liquid crystal display element 73 to form an optical image of the raster pattern of the designated color. . As a result, the fluctuation of the reference voltage Vcom of the counter electrode caused by the change over time caused by the liquid crystal display element at the position of the optical sensor 10 installed on the outer peripheral edge (outside the effective display area) of the screen 20 is improved. A raster pattern of a designated color (here, R color) for adjustment to a state (a state where flicker is not visually recognized) is displayed. In this embodiment, a three-plate type liquid crystal display element is assumed. However, the present invention is not limited to this, and the present embodiment can be applied to one or more liquid crystal display elements.

  In the case of the three-plate type, flicker adjustment is performed for each of the R panel, G panel, and B panel. Therefore, when the R panel is adjusted, an R color raster pattern is displayed on all the optical sensors 10. Similarly, the raster pattern of each color is displayed on the G panel and the B panel.

  Next, the detection signal of the designated color (here, R color) output from the optical sensor 10 is input to the signal processing circuit 30. As shown in FIG. 7, the signal processing circuit 30 includes a high-pass filter 31, a low-pass filter 32, and an A / D converter 33. The detection signals detected by the optical sensors 10 are added and input to the signal processing circuit 30. The detection signal input to the signal processing circuit 30 is input to the high pass filter 31, the DC component is removed, and only the AC component is extracted and input to the low pass filter 32. From the detection signal input to the low-pass filter 32, noise contained in the detection signal is removed and input to the A / D converter 33. In the A / D converter, the analog detection signal output from the low-pass filter 32 is digitally converted at a predetermined sampling period and output.

When the digital detection signal A / D converted from the signal processing circuit 30 is input to the control circuit 40, the control circuit 40 causes the drive circuit 50 to change over time due to the liquid crystal display element 73 by the input digital detection signal. In order to adjust the fluctuation of the reference voltage Vcom of the counter electrode caused by the change to a good state, the voltage (digital detection signal voltage) DV _{pp of} the input digital detection signal and the digital flicker limit voltage VD previously stored in the memory _{The FLs} are compared (S502). If the digital detection signal voltage DV _pp is less than or equal to the digital flicker limit voltage DV _FL (that is, if it is Yes (hereinafter abbreviated as “Y”)), flicker is not visually recognized, so the first color is the R color. The flicker adjustment of the corresponding liquid crystal display element is completed, and the process goes to S509. If the digital detection signal voltage DV _pp is not less than or equal to the digital flicker limit voltage DV _FL (that is, if the determination in S502 is No (hereinafter abbreviated as “N”)), the digital detection signal voltage is first increased in the direction of increasing the currently set reference voltage. The new digital reference voltage value changed in the voltage step DVstep is sent to the drive circuit 50, and the reference voltage of the counter electrode is slightly changed by the drive circuit 50 (S503). In S504, the digital detection signal voltage DV _pp (u) after the new change is compared with the digital detection signal voltage DV _pp before the change, and if the digital detection signal voltage VD _pp (u) after the new change is small, In S505, the digital detection signal voltage DV _pp (u) is compared with the digital flicker limit voltage DV _FL . If the digital detection signal voltage DV _pp (u) is not less than or equal to the digital flicker limit voltage DV _FL , the changed reference voltage Vcom is further increased by one step in the digital voltage step DVstep in S506, and the process returns to S505 to return to the digital detection signal voltage DV until _pp (u) is equal to or less than the digital flicker limit voltage _{DV FL,} repeated S505, S506. If the digital detection signal voltage DV _pp (u) is equal to or lower than the digital flicker limit voltage DV _{FL in} S505, the new digital reference voltage DVcom corresponding to the reference voltage at that time is stored as the currently set reference voltage of the R color liquid crystal display element. And go to S509.

If the digital detection signal voltage DV _pp (u) after the new change is larger than the digital detection signal voltage DV _pp before the change in S504, the process proceeds to S507. Conversely, in S507, the current set reference voltage is changed to the digital voltage step DVstep. The digital detection signal voltage DV _pp (d) after the new change is compared with the digital flicker limit voltage DV _FL in step S508. If the digital detection signal voltage DV _pp (d) is not equal to or less than the digital flicker limit voltage DV _FL , the process returns to S507, and S507 and S508 are performed until the digital detection signal voltage DV _pp (d) becomes equal to or less than the digital flicker limit voltage DV _FL. repeat. If the digital detection signal voltage DV _pp (d) is equal to or lower than the digital flicker limit voltage DV _{FL in} S508, the new digital reference voltage DVcom corresponding to the reference voltage at that time is stored as the currently set reference voltage of the R color liquid crystal display element. And go to S509.

  With the above processing, the flicker adjustment of the liquid crystal display element corresponding to the R color which is the first color is completed.

  In step S509, it is determined whether the flicker adjustment of the liquid crystal display element corresponding to the second color (G color in this case) has been completed. If it is N, the color of the raster pattern is changed to the second color G in S510, and the process returns to S502. Similarly to the R color, flicker adjustment of the G color liquid crystal display element is performed in S502 to S508. If the determination in S509 is Y, the flicker adjustment of the liquid crystal display element corresponding to the second color G has been completed, and the process proceeds to S511, where the liquid crystal display corresponding to the third color B color is displayed. It is determined whether the flicker adjustment of the element is completed. If N, the raster pattern color is changed to the third color B in S512, and the process returns to S502. Similarly to the R and G colors, the flicker adjustment of the B liquid crystal display element is performed in S502 to S508. Do. If the determination in S511 is Y, flicker adjustment for all colors has been completed, and the flicker adjustment processing is terminated.

  In this embodiment, since the position of the photosensor is the outer peripheral edge of the screen, the photosensor can be easily installed. Further, the outer peripheral edge of the screen is a place that is not easily affected by heat from a heat source (for example, a light source). Therefore, the sensor installed on the outer peripheral edge of the screen does not need to use an optical sensor having a high heat-resistant temperature, and a relatively inexpensive optical sensor can be used.

  As described above, according to the present embodiment, the fluctuation of the reference voltage of the counter electrode caused by the change with time due to the liquid crystal display element can be automatically adjusted to a good state (that is, the flicker is not visually recognized). .

  Needless to say, the liquid crystal display device according to the present invention can be applied to a simple matrix system as well as an active matrix type liquid crystal display element.

  In the first embodiment, the flicker adjustment of the liquid crystal display element corresponding to the first color (for example, R color) is performed, and then the flicker adjustment of the liquid crystal display element corresponding to the second color (for example, G color) is performed. Finally, the serial adjustment process is performed to adjust the flicker of the liquid crystal display element corresponding to the third color (for example, B color), but this takes time to adjust the flicker. A second embodiment in which flicker adjustment of each color is performed in parallel to shorten the adjustment time will be described below.

  FIG. 2 is a block diagram of a liquid crystal display device according to the second embodiment. In FIG. 2, elements having the same functions as those in FIG. 1 are denoted by the same reference numerals, and redundant description thereof is omitted.

  In FIG. 2, optical sensors 10 r, 10 g, and 10 b that detect image light corresponding to raster patterns of different colored lights (for example, R, G, and B) are disposed on the outer peripheral edge of the screen 20. Detection signals detected by these optical sensors 10r, 10g, and 10b are input to the signal processing circuit 130, respectively.

  The signal processing circuit 130 includes three signal processing circuits 30 described in FIG. 1, and includes a signal processing circuit 30r that processes a detection signal from the optical sensor 10r and a signal processing circuit that processes the detection signal from the optical sensor 10g. 30g and a signal processing circuit 30b for processing a detection signal from the optical sensor 10b. Each detection signal from each optical sensor 10x input to each signal processing circuit 30x (hereinafter, “x” is used to indicate an arbitrary one of r, g, and b) is a high-pass filter. Input to 31x, DC component is removed and only AC component is extracted and input to each low pass filter 32x. The detection signal input to each low-pass filter 32x is input to each A / D converter 33x after removing noise contained in the detection signal. Each A / D converter 33x converts the detection signal output from the low-pass filter 32x into a digital signal at a predetermined sampling period and outputs the digital signal to the control circuit 40A.

  In the drive circuit 50A of this embodiment, the color of the raster pattern, which is a built-in test pattern, is a color corresponding to the optical sensor 10x for each corresponding region irradiated to the position of the optical sensor 10x. Is different from the first embodiment in that a red raster pattern, a green raster pattern on the optical sensor 10g, and a blue raster pattern on the optical sensor 10b are simultaneously irradiated.

When the switch 90 is operated, the control circuit 40A starts flicker adjustment as in the first embodiment. In this embodiment, the drive circuit 50A uses the raster pattern of each color at the position of each photosensor 10x. Irradiate. Then, the control circuit 40A receives each digital detection signal from each photosensor 10X that has been signal-processed by the signal processing circuit 130, and receives each liquid crystal display element caused by a change over time caused by each liquid crystal display element 73. counter for each change of the reference voltage of the electrode is adjusted in good condition, in parallel in time, the counter electrodes of the liquid crystal display device which is stored in advance in the memory and the digital detection signal voltage DV _pp entered the the digital flicker limit voltage DV _FL compared respectively, performs the feedback control so that the digital detection signal voltage is less than the digital flicker limit voltage DV _FL.

  A series of processing of feedback is the same as that of the first embodiment except that it is performed in parallel for each liquid crystal display element of each color, and detailed description thereof is omitted.

As described above, in this embodiment, the optical sensors 10x corresponding to the respective colors are arranged on the outer peripheral edge of the screen 20, and the detection signals detected by the optical sensors 10x can be simultaneously processed in parallel. Since each of the optical sensors 10x is simultaneously irradiated with a corresponding raster pattern of a different color, each digital detection signal voltage is based on the detection signal detected by each optical sensor 10x. There it is possible to batch processing for performing feedback control so as to be less digital flicker limit voltage DV _FL, compared with the case of the first embodiment, it is possible to shorten the adjustment time.

  In the first and second embodiments, the optical sensor 10 is arranged on the outer peripheral edge of the screen 20, but the present invention is not limited to this. In the first and second embodiments, since the position of the photosensor is the outer peripheral edge of the screen, the amount of light received by the photosensor is small, and the output signal amplitude of the photosensor is small. Therefore, in the third embodiment, an embodiment in which the optical sensor 10 is provided on the back surface of a rear mirror (folding mirror) used in the rear projection type liquid crystal display device will be described with reference to FIG.

  FIG. 3 is a schematic configuration diagram of a rear mirror showing a third embodiment. FIG. 3A is an image view when the rear mirror 80 is viewed from the front, and FIG. 3B is a rear view of the rear mirror. It is an image figure of time.

  In the present embodiment, as shown in FIG. 3, the optical sensor 10 is attached to the back surface of the rear mirror 80 that reflects (folds back) the light projected from the optical system 70 in the screen direction. A light incident port 81 that guides light to the optical sensor 10 is provided at the reflection surface position on the surface side corresponding to the arrangement position of the optical sensor 10 (this position is in the effective display area) as shown in FIG. As shown, a metal vapor deposition film 82 that forms the reflecting surface of the rear mirror 80 is provided without vaporizing only that portion. Note that the size of the light incident port 81 is preferably small. Preferably, it should be 1 pixel or less. The reason why the number of pixels is 1 pixel or less is to reduce the shadow area on the screen caused by non-reflection at the light entrance, making it difficult to visually recognize the shadow, and minimizing the decrease in luminance. Then, in the process in which the raster pattern generated by the drive circuit 50 is folded back by the rear mirror 80 via the optical system 70 and projected onto the screen 20, the light sensor 10 detects the luminance of the liquid crystal display element. It is.

  In addition, since the photosensor is disposed on the back surface of the screen in this embodiment, there is an effect that the shadow caused by the wiring of the photosensor is not projected on the screen.

  In this embodiment, unlike the first and second embodiments, the photosensor is provided in the effective display area of the projected image from the liquid crystal display element, not in the peripheral edge portion of the screen. Since the amount of light to be generated is greater than the peripheral edge of the screen, the output signal amplitude of the optical sensor is increased, the brightness of the projected image can be detected with high accuracy, and the adjustment accuracy of flicker adjustment can be increased.

  In this embodiment, flicker adjustment is the same as that in the first embodiment, and a detailed description thereof is omitted. It is also obvious that the flicker adjustment described in the second embodiment can be applied if a plurality of, for example, three light incident ports 81 for detecting R light, G light, and B light are provided. Is also omitted.

  In the third embodiment, the optical sensor is provided on the rear surface of the rear mirror in the middle of the optical path from the liquid crystal display element to the screen. However, the arrangement location of the optical sensor is not limited to this. In this embodiment, the optical sensor is disposed in the projection lens unit 200. Hereinafter, the fourth embodiment will be described using a rear projection television as an example.

  FIG. 8 is a schematic configuration diagram of a rear projection television. As shown in FIG. 8, in the rear projection television, an optical image is formed on a liquid crystal display element in the optical engine 201 in accordance with an input video signal (not shown), and light is emitted from the light source to the optical image. Is enlarged and projected by the projection lens unit 200, and the input video signal is displayed on the screen 20 via the rear mirror 80.

  FIG. 9 is a schematic configuration diagram of a projection lens unit and an optical engine showing a fourth embodiment. As shown in FIG. 9, the projection lens unit 200 in this embodiment includes a first projection lens system 100a and a second projection lens system 100b. With this configuration, the difference in the projection distance due to the inch size can be dealt with, for example, by exchanging only the second projection lens unit. A reflecting mirror 100c is disposed between the two projection lens units.

  In this embodiment, the optical sensor is disposed in the projection lens unit 200. The reason will be described. The optical sensor can detect with higher sensitivity as the amount of light detected increases, and the amount of light attenuates as the optical distance from the light source increases. Therefore, it is preferable to arrange the sensor as close to the light source as possible for highly sensitive light detection, and the optical sensor is arranged in the projection lens unit closer to the light source than the optical sensor position described in Examples 1 to 3. As a result, flicker can be detected with higher sensitivity.

  Further, in the present application, since flicker appearing on the liquid crystal display element is detected, it is conceivable to arrange an optical sensor immediately after the liquid crystal display element in the optical engine 201. However, light detection before combining the R, G, and B light requires three optical sensors for R, G, and B. Furthermore, if an optical sensor is disposed in the optical path before photosynthesis, the balance of the light amounts of R, G, and B (white balance) may be lost, and the necessary light amounts may not be obtained for each color. Therefore, by disposing the optical sensor in the projection lens 200 after combining the R, G, and B light, flicker can be detected by one sensor, and it is necessary to adjust the new R, G, and B light amounts. In addition, flicker detection can be realized with a simple configuration.

  In addition, the location of the optical sensor in the projection lens is preferably a location where the projected image is not focused, for example, it may be installed in a reflecting mirror between projection lenses, between projection lenses, or a projection lens. By installing the optical sensor in a place where the focus is not achieved, it is possible to reduce the influence of the shadow cast on the screen, and to reduce discomfort given to the user viewing the screen. In addition, when the optical sensor is installed at a place where the focus is not achieved, the optical sensor can be arranged in the effective display area of the projection image.

  When an optical sensor is installed on the reflecting mirror 100c, an optical sensor (not shown) is provided on the back surface of the reflecting mirror 100c as in the third embodiment. At that time, the size of the light entrance (not shown) provided on the reflection surface on the surface side of the reflecting mirror 100c that guides the light to the optical sensor is preferably as small as possible. In addition, although the position of the optical sensor is arranged on the back surface of the reflecting mirror, it may be the front surface.

  In addition, when the optical sensor is installed between the projection lenses, there is no work for installing the optical sensor on the optical component or the like, and it is possible to install the optical sensor by, for example, an operation that is screwed to the structural component.

  In addition, when an optical sensor is installed on the projection lens, a portion that is out of focus as much as possible is selected. By doing so, it is possible to reduce the influence of the shadow that appears on the screen.

  Further, in the present embodiment, the rear projection television (rear projection type liquid crystal display device) has been described as an example. However, the present invention is not limited to this and can be applied to a front projection type liquid crystal display device.

  Further, in the present embodiment, the projection lens unit has been described as an example constituted by two projection lens systems. However, the present invention is not limited to this, and the projection lens unit is constituted by one or a plurality of projection lens systems. It may be a thing.

  In the embodiment, the video display device uses a liquid crystal display element as a display element, but the present invention is not limited to this.

  In the present embodiment, flicker adjustment is the same as in the first embodiment, as in the third embodiment, and detailed description thereof is omitted. It is also obvious that the flicker adjustment described in the second embodiment can be applied if a plurality of, for example, three light incident ports 81 for detecting R light, G light, and B light are provided. Is also omitted.

The block block diagram of the liquid crystal display device which shows a 1st Example. The block block diagram of the liquid crystal display device which shows a 2nd Example. The schematic block diagram of the rear-view mirror which shows a 3rd Example. The figure showing the control flow of a control circuit. The figure showing the inversion signal input into a liquid crystal display element. The figure showing the detection signal of an optical sensor. The block diagram of a signal processing circuit. The schematic block diagram of a projection television. The schematic block diagram of the projection lens which shows a 4th Example.

Explanation of symbols

10 optical sensors, 20 screens, 30 signal processing circuits, 40 control circuits, 50 drive circuits, 60 video processing circuits, 70 optical systems, 72 light sources, 73 liquid crystal display elements, 80 rear-view mirrors, 81 light incident ports, 82 vapor deposition films, 90 switch, 200 projection lens, 130 signal processing circuit,

Claims (14)

A video display device that irradiates a display element with light from a light source, forms an optical image according to a video signal, and projects an enlarged image.
A reflecting mirror for reflecting the light after irradiation to the display element;
An optical sensor for detecting the light intensity after irradiation on the display element;
A drive circuit for driving the display element;
A control circuit for controlling the drive circuit based on the light intensity detected by the optical sensor,
The video display device, wherein the optical sensor is provided in the reflecting mirror. The video display device according to claim 1,
A plurality of lenses for enlarging and projecting the optical image;
The video display device, wherein the reflecting mirror is disposed on an optical path between the plurality of projection lenses. The video display device according to claim 1,
A display unit that images the light reflected by the reflecting mirror and displays the video signal;
The video display device, wherein the reflecting mirror is disposed on a back surface of an image display surface of the display unit. The video display device according to claim 1,
The display device is a liquid crystal display device. The video display device according to claim 2 or 3,
The video display device, wherein the optical sensor is disposed on a back surface of a reflecting surface of the reflecting mirror. The video display device according to claim 2 or 3,
The reflecting mirror has an entrance through which light enters,
The image display device, wherein the optical sensor detects light intensity that has passed through the incident port. The video display device according to claim 6,
An image display device characterized in that the size of the entrance is 1 pixel or less. A video display device that irradiates a display element with light from a light source, forms an optical image according to a video signal, and projects an enlarged image.
A screen for imaging the enlarged and projected light to display the video signal;
An optical sensor for detecting the light intensity after irradiation on the display element;
A drive circuit for driving the display element;
A control circuit for controlling the drive circuit based on the light intensity detected by the optical sensor,
The video display device, wherein the optical sensor is provided on an outer peripheral edge of the screen. The video display device according to claim 8,
The video display device characterized in that the outer peripheral edge of the display unit is outside the effective display area of the display unit. The video display device according to claim 7,
A plurality of the optical sensors are provided on the outer peripheral edge of the display unit. A light source;
A display element that irradiates light from a light source to form an optical image according to a video signal;
A projection lens unit that magnifies and projects the optical image;
An optical sensor for detecting the light intensity after irradiation on the display element;
A drive circuit for driving the display element;
A control circuit for controlling the drive circuit based on the light intensity detected by the optical sensor,
The video display device, wherein the optical sensor is provided in the projection lens unit. The video display device according to claim 11,
A reflection mirror that is disposed in the projection lens unit and reflects the light after irradiation to the display element;
The video display device, wherein the optical sensor is disposed on the reflecting mirror. The video display device according to claim 11,
The projection lens is composed of a plurality of projection lenses,
The video display device, wherein the optical sensor is disposed between the plurality of projection lenses. The video display device according to claim 11,
The image display device, wherein the optical sensor is installed in a projection lens in the projection lens unit.

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